Related papers: Parapositronium Decay and Dispersion Relations
We present the calculation of the mixed two-loop QCD/electroweak corrections to hadronic W boson decays within the Standard Model. The optical theorem is applied to the W boson two-point function. The multi-scale integrals are computed with…
Quarkonium decays are studied in the charmonium model. Relativistic corrections, higher-order perturbative QCD corrections and non- perturbative contributions are discussed. Recent measurements of charmonium annihilation rates are used to…
Contributions to the decay rates of P-wave charmonium states that are proportional to $n_f \alpha_s^3$, where $n_f$ is the number of flavors of light quarks, are calculated in the framework of nonrelativistic QCD using the threshold…
By means of the universal unitary and analytic model of electromagnetic structure of hadrons the two-photon decay rates of P=pi^0, eta, eta' mesons are determined in an alternative way from data on their transition form factors.
Correlations among hadrons with the same electric charge produced in Z$^0$ decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order…
We discuss various tests of the factorization hypothesis making use of the close relationship between semi-leptonic and factorized nonleptonic decay amplitudes. It is pointed out that factorization leads to truely model-independent…
We provide succinct covariant amplitude decompositions of 2-body weak hadronic decays, with which to compare data, including exclusive rates, helicity amplitudes and polarizations. For weak decays, the systematic dependence of these…
We compare two existing approaches to calculating the decay of molecular quarkonium states to conventional quarkonia in effective field theory, using $X(3872) \to \chi_{cJ} \pi^0$ as an example. In one approach the decay of the molecular…
We use the Bodwin-Braaten-Lepage factorization scheme to separate the long- and short-distance factors that contribute to the decay rates of $\Upsilon$, $\eta_b$ (S-wave) and $\chi_b$,$h_b$ (P-wave). The long distance matrix elements are…
We present a detailed calculation of channeling radiation of planar-channeled positrons from crystal targets in the framework of our approach, which was proposed recently. In contrast to previous calculations of channeling radiation in…
Using NLL values for Wilson coefficients and including the contributions from the penguin diagrams, we estimate the amount of nonfactorization in two-body hadronic B decays. Also, we investigate the model dependence of the nonfactorization…
Using the Bodwin--Braaten--Lepage factorization theorem in heavy quarkonium decay and production processes, we calculated matrix elements associated with S- and P-wave bottomonium decays via lattice QCD simulation methods. In this work, we…
The factorization of hard and soft contributions into the hadronic decays of B_c meson at large recoils is explored in order to evaluate the decay rates into the S, P and D-wave charmonia associated with rho and pi. The constraints of…
We apply a subtracted dispersion relation formalism with the aim to improve predictions for the two-photon exchange corrections to elastic electron-proton scattering observables at finite momentum transfers. We study the formalism on the…
We discuss few selected topics related to the calculation of hadronic amplitudes relevant for two-body non-leptonic B decays.
Ongoing improvements in the measurement of positronium transition intervals motivate the calculation of the $O(m \alpha^7)$ corrections to these intervals. In this work we focus on corrections to the spin-singlet parapositronium energies…
Estimating decay parameters in lattice simulations is a computationally demanding problem, requiring several volumes and momenta. We explore an alternative approach, where the transition amplitude can be extracted from the spectral…
We calculate the decay of pionium atoms into two photons. The pion polarizability gives rise to a 10% correction to the corresponding decay width for pointlike pions. This opens the possibility to obtain the difference between the electric…
The pionium decay width is evaluated in the framework of chiral perturbation theory and the relativistic bound state formalism of constraint theory. Corrections of order O(\alpha) are calculated with respect to the conventional lowest-order…
The calculation of the R-ratio of electron-positron annihilation into hadrons is discussed. The method, which enables one to properly account for all the effects due to continuation of the spacelike perturbative results into the timelike…